A hybrid vehicle adopts two different power sources at the same time, and according to different connection manners of a power system, there are mainly three types of structure: series, parallel, parallel and series.
The characteristic of the series structure is to combine the output power by electricity; the engine directly drives the generator to charge the energy storage device and the motor; the motor is used to drive the wheels. The characteristic of the parallel structure is to combine output power by mechanical energy; the engine is connected with the drive shaft; the motor may operate as the motor and the generator simultaneously to balance the load of the engine. The driving modes of the series structure and parallel structure are respectively single, and can not fully exert the advantage of the hybrid power driving system.
Currently, the hybrid power driving system used in prior art is usually the series and parallel type.
For one of the current series and parallel mode, power is distributed to every power unit by a planet gear mechanism. In this mechanism, the engine is connected with a planet carrier; a part of the mechanical energy of the engine is transferred into electricity by a first motor to provide electricity to a second motor or to charge the energy storage device; another part of the mechanical energy directly acts on a gear ring. Meanwhile, the second motor is connected with the gear ring to provide a part of power and torque.
For another series and parallel mode in prior art, power is distributed to every power unit by a clutch, such as those disclosed in U.S. Pat. No. 6,209,672B1. In this structure, the engine is connected to a first motor; the first motor and the second motor are connected through the clutch; the vehicle power is transferred to wheels through an output shaft of the second motor. By controlling the engage and disengage of the clutch, a plurality of running modes are achieved.
In above mentioned two series and parallel modes, generally there are two motors; sometimes a transmission is needed. For the first mode, the planet gear mechanism is needed. So the structure is complicated occupying more space, which counts against the vehicle layout and reduction of vehicle weight.
For another series and parallel mode in prior art, power is distributed to each power unit by a clutch and a transmission.
For example, US Patent Application No. 2006/0254837A1 discloses a hybrid power driving system. The engine is connected to the first input shaft of the transmission by a clutch; a motor is connected to the second input shaft of the transmission. The power of the engine and/or the motor is transferred to the wheels through an output shaft of the transmission. The first input shaft and the second input shaft may be two terminals of a common main shaft which penetrates through the transmission, or may be two separate shafts which are jointed together. When the clutch is engaged, the engine can drive the vehicle separately (the engine may also used to control the motor to generate electricity at this time); or the engine and the motor are connected in paralleled to drive the vehicle. When the clutch is disengaged, the motor drives the vehicle separately. In this solution, the power distribution of each power unit is mainly utilized by the clutch. The transmission functions as a traditional role of speed variation. Thus, the driving mode of this driving system is relatively simple. In addition, the transmission is too huge which is disadvantageous for reducing the total vehicle weight.
In addition, U.S. Pat. Nos. 5,337,848 and 6,019,698 also disclose a similar structure, that is, a clutch is configured between an engine and a transmission. Different driving modes of the vehicle are realized by engagement and the disengagement of the clutch. Moreover, the power of the engine and the motor can be coupled by the transmission and then transferred to wheels. There is the same problem in this structure. That is, the driving mode is relatively simple, and the transmission is too huge which is disadvantageous for reducing the total vehicle weight.